A high-efficiency, reliable compact synchronous motor, which is capable of securely changing from starting operation to synchronous operation, has been developed. In the synchronous motor, alternate current supplied from an AC power source is switching-controlled and full-wave rectified, by a bridge rectifier circuit, for the starting operation. At that time, for example, only an A coil of a motor coil, which is divided into the A coil and a B coil by an intermediate tap, is energized to pass relatively high current for the starting operation, and positive or negative energizing range of the rectified current is switching-controlled so as to converge the current waveform to one side. When number of revolutions of a magnet rotor is in the vicinity of a synchronous number of revolutions with respect to a power source frequency, an operation changing switch is actuated to transfer the operation to synchronous operation (see Patent Document 1).
Patent Document 1: Japanese Patent No. 3050851